Key for a keyboard which may be made more or less difficult to depress

ABSTRACT

A key for a keyboard such as is used in control stations for computers, teletypewriters, and other machines, in which keys are used to transmit or record intelligence, and which may have one or more selected keys that may be rendered difficult to press, which pressure is substantially more than the normal operating pressure of the keys. Each key is operatively associated with a magnetizable disc and a permanent magnet and an electromagnet which provide the biasing force so as to block the key. The key is also spring-biased so that it may initially be pressed for a first distance.

United States Patent [72] Inventor Hermann Plleninger Neugilchlng,Germany [211 App]. No. 777,298

[22] Filed Nov. 20, 1968 [45] Patented Dec. 14, 1971 73] AssigneeSiemens Aktiengesellsehalt Berlin and Munich, Germany [32] Priority Nov.29, 1967 3 3 1 Germany [54] KEY FOR A KEYBOARD WHICH MAY BE MADE MORE0!! LESS DIFFICULT T0 DEPRESS 2 Claims, 4 Drawing F las.

[52] US. Cl 197/107,

[5 I] int. Cl 84115/22 [50] Field 0! Search 197/98, 102,103, 104,107,108, llO

[ 56] Relerences Cited UNITED STATES PATENTS 3,528,535 I 9/1970Bodenstein et al. l 97/l07 I 2,665,336 1 1954 Saykay 197/9sux 3,197,0107/1965 Seibel 197/9sx 3,233,061 2/1966 Jones... 197/9'sux 3,249,1995/1966 Jones 197/98X 3,251,962 5/1966 Jones 197/9sx 3,305,062 2/1967Kittredge. 197/98X 3,454,717 7/1969 Peters 197/107x 3,457,368 7/1969Houcke 197/9sx FOREIGN PATENTS 1,277,523 10 1961 France 197/98 1 PrimaryExaminer-Ernest T. Wright, Jr.

Attorney-Hill, Shennan, Meroni, Gross & Simpson ABSTRACT: A key for akeyboard such as is used in control stations for computers,teletypewriters, and other machines, in

which keys are used to transmit or record intelligence, and

which may have one or more selected keys that may be i rendereddifficult to press, which pressure is substantially more than the normaloperating pressure of the keys. Each key is operatively associated witha magnetizable disc and a permanent magnet and an electromagnet whichprovide the biasing force so as to block the key. The key is alsospringbiased so that it may initially be pressed for a first distance.

Patented an. M, 1971 K s DISTACE @IIP M38 CURRENT SOURCE K DISTANCEDESTANCE QNVENTOR HERMANN PLIIENIMQER ATTORNEYS KEY FOR A KEYBOARD WHICHMAY BE MADE MUM OR LESS DIFFICULT T DEPRESS BACKGROUND OF THE INVENTION1 Field of the Invention This invention relates in general to keyboardsand in particular to a keyboard having keys that may be selectivelydepressed to record or transmit intelligence such as used intypewriters, teletypewriters, feeder machines for computers, controlpanels for keypunch equipment and other similar applications.

2. Description of the Prior Art It is at times desirable and necessaryto block certain keys on a keyboard so that particular keys cannot beenergized or which will he energized under conditions where the operatorknows that he is. actuating a key that is heavier biased than usual.Prior blocking means for keys have consisted of mechanical locks whichengage the keys to prevent the selected keys from being depressed.

SUMMARY OF THE INVENTlON The present invention relates to a means andapparatus for selectively blocking certain keys on a keyboard in whichthe key may be depressed for a first portion of its travel beforeencountering a strong blocking force. A substantial amount of force maybe utilized to overcome the blocking force if desired by the operator toactuate the key.

The key is operatively associated with a magnetizable disk and apermanent magnet and an electromagnet which provides a biasing force soas to block the key. The key also is spring biased so that it may beinitially depressed for a first distance and which engages a substantialresisting force after the spring has been depressed that can only beovercome by substantial force on the key when the electromagnet isactivated. A further depression of the key moves a permanent magnetabout a magnetizable pin that energizes a switch to ac tuate an externalcircuit in response to the depression of the key.

When the key is released the biasing springs return it to the upposition and the magnetizable pin allows the controlled contacts to openand-the key to return to its initial position.

Other and further objects of the invention will become apparent to thoseskilled 'in the art from the following detailed description of thesingle sheet of drawing which shows the preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of a keyaccording to this inventron;

FIG. 2 is a graph of force versus distance plot for the key of FIG. 1when it is unblocked without a biasing spring;

FIG. 3 is a force versus distance plot of the key when. it is blocked;and

FIG. d is a force versus distance plot of the key of FIG. I for astructure which does not have biasing springs.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. I illustrates a keyaccording to this invention wherein a housing I has a generallycylindrical outer portion lb and an opening 2% lonned in one end with aneck la in which a key 2 is inserted. The key 2. has a flanged operatingportion 2a which is connected to a cylindrical neck portion 2b ofnonmagnetic material and which has a diameter of a size such that itfits within the opening of the portion 1a. A lower extending portion 2cof smaller diameter extends from the portion 2b and is attached to adisk .member 2d that has an outer diameter equal to the inner diameterof the housing portion lb. The disk 2d and the lower portion of theportion 2c is fonned with an opening 19 into which the end of amagnetizable pin 9 may be received. The pin 9 extends through an opening21 in the lower portion of the housing portion 1b and into a sealedswitching chamber formed by the conducting housing 7. The

housing 7 has an opening 36 in which a glass seal 8 surrounds the pin 9.The lower end of the pin 9' is mounted adjacent an electrical contact l0which has its other end connected to the conducting housing 7. An inputterminal 11d is electrically connected to the conducting housing 7 toform one terminal of an electrical output circuit. The pin 9 isinsulated by glass seal 8 from the housing portion 7 and the housingportion lb and a conductor 22 extends through an insulated opening 37 inthe wall of the housing 11b and is connected to a second output terminal113. Thus, when the flexible contact 10 engages the pin 9 the electricalcircuit is closed between. the contacts 13 and 14. The flexible contactI0 does not engage the pin 9 unless the key 2 is depressed but thecontact MI is flexible and can be drawn by magnetic force to engage theend of pin 9 when the key 2 is depressed.

A spring ll is mounted between the end wall 23 of the housing portion 1band the disk 2d.

A toroid formed permanent magnet s is mounted about the portion 2::between the disk 2d and a second disk 5. A spiral spring 112 is mountedbetween the disk 5 and the lower portion 2: of the neck portion 2b ofthe key 2. An electromagnet 38 is mounted in the housing portion lbbetween the portion Ia and the disk 5 and comprises a core form d thatis opened on the portion facing the disk 5 and a winding; 3 is wound tinthe core form 4. Leads 16 and 17 extend from the winding 3 and areinsulated from the housing portion llb. A switch SI is mounted in theline 117 and a current source lid is connected to the switch SI and thelead 117. A knob 2d is connected to a shaft 26 for adjusting the currentin the winding 3 when the switch Si is closed.

The flange 2a and neck portion 2b are non magnetic. The pin 9 is ofmagnetizable material and is electrically conductive so as to conductcurrent when the switch contact engages it. The toroid magnet 6 isformed of permanent magnetic material and is magnetized radially.

In operation, if the switch SI is open so that the key 2 is not blockedor partly blocked, movement of the key 2 is substantially a linearfunction of the spring 12 until the lower portion of the member 2c andthe magnet s are forced to pass over the upper end of the pin 9 thuscausing the magnetic flux of the permanent magnet 6 to attract thecontact ill) to the mag netizable pin 9 and thus close the circuitbetween the contacts 113 and I4.

If the switch S1 is closed the electromagnetic force formed by thewinding 3 willhold the permanent magnet 6 against the disk 5 and thedisk 3 against the core form l. as the key 2 is depressed. Thus the keyportion 2a will depress and compress spring 12 until it has beencompletely depressed. When electromagnet 38 is not energized the spring112 does not have an effect because nov relative movement occurs betweenthe key 2, spring I2, adherence disk 5 and permanent magnet d. The key 2can be pressed downwardly against the force of the recoil spring Ill.Thus, the permanent magnet 65 moves down over pin 9 causing more andmore mapretic flux to flow through pin 9 and this concentration of fluxcauses flexible switch contact ill to move to engage the pin 3 closingthe circuit between contacts I3 and M. When the key flange portion 2a isreleased, the key 2 and also the permanent magnet 6 is moved to itsinitial position by the recoil spring I1 and flexible switch contact illmoves out of engagement with pin 9.

With a blocked key 2, the electromagnet 38 is energized and the pressurespring I2 is supported by the adherence disk 5 which adheres to the coreform 4 of the electromagnet 38. [fr

now the key 2. is pressed further, the force of the recoil spring 111and the force of the spring 112 must be overcome. The spring 112 issuitably pretensioned so that it produces a force slightly below theholding force of the adherence disk 5 with electromagnet 38 and, as seenin FIG. 3, the hatched area becomes as large as possible below the powercurve of FIG. 3. The pressure spring 12 does not change the blockageforce, rather it is determined by the holding force of the adherencedisk 5 with the electromagnet 38. The blockage energy, however, causesan increased key force which is effective over a larger key distance. Acomparison of FIGS. 2 and 3 which illultrate a force-distance diagramfor an unblocked key 2 without spring 12, and a diagram for a blockedkey 2 with spring 12, respectively, shows that not only the blockageforce but, in particular, the blockage energy (force times distance) isessentially higher with blocked keys 2. If the spring 12 were omitted,mere blockage energy would result until the point that contact is made(K). This blockage energy is illustrated in FIG. 4 by hatching. Thiscondition is illustrated in FIG. 3 and it is to be particularly notedthat much greater force is required to depress the key 2 when the switchS1 is closed than is required when the switch S1 is open, for example,the force illustrated in FIG. 3 is substantially more than the forceillustrated in FIG. 2.

If the spring 12 were eliminated only the blocking energy from theelectromagnet 38 would exist.

The knob 24 and shaft 26 allows the current source 18 to be adjusted toadjust the amount of current in the winding 3. With the key 2 in theposition shown in FIG. 1 only a small amount of magnetic flux flowsthrough the pin 9 and this is insufficient to cause the contact 10 toengage the pin 9. When the key 2 is pressed downwardly against the forceof the recoil spring 11 and the spiral spring 12 the holding magneticforce from the electromagnet 38 will be felt. it the key 2 is depressedfurther the completely compressed spring 12 causes the adherence disk 5and magnet 6 to release from the electromagnetic core form 4 and themagnet 6 will move close to the flux guide pin 9 thus causing the fluxin the pin 9 to increase to attract the flexible contact 10 and completethe circuit between contacts 13 and 14.

The recoil spring 11 and spring 12 will return the key 2 and the magnet6 to the position shown in FIG. I when the key 2 is released.

Since the holding force of the permanent magnet 6 is a function of thesize of the adherence surface and the amount of magnetization of themagnet 6, the key pressure may be varied by correspondingly varyingthese two factors thereby effecting the switching operation of thecontact 10. The blocking force can also be controlled by the adjustmentof the current source 18 through the knob 24.

The operator becomes accustomed to the unblocked tension on the keys 2.When it is desired to inhibit or block certain the keys 2 the switch S1is closed and the operator immediately is aware of the increase force onthe blocked keys 2. The keys 2 may still be depressed by exertingapproximately four times the normal closing force as shown by comparingFIG. 2 and FIG. 3 but the keys 2 would be depressed when blocked onlywhen this is particularly desired by the operator and the operator wouldrealize that he was depressing a blocked key 2.

The disks 5 and 2d and toroid magnet 6 are loosely mounted in thehousing 1. The electromagnet 38 comprising .coil 3 and core form 4 arefixed to the housing 1.

FIGS. 2, 3 and 4 are force versus displacement plots. The force P" isthe force required to move the key 2. The distance 8" is thedisplacement of the key 2. "K" indicates the displacement at which theflexible contact 10 engages pin 9 to complete the electrical circuitbetween contacts 13 and 14.

The switch S1 may be actuated manually or automatically.

It is seen that this invention provides a simple and inexpensiveapparatus for selectively blocking keys of a keyboard.

Although I have herein set forth my invention with respect to certainspecific principles and details thereof, it will be understood thatthese may be varied without departing from the spirit and scope of theinvention as set forth in the hereunto appended claims.

I claim as my invention:

1. A key for a keyboard for actuating a signal means comprising ahousing, a key supported for longitudinal movement in said housing andhaving a first portion which extends from said housing; an electromagnetfixed to said housing at one end thereof and said key extending throughsaid electromagnet; and adherence disk loosely mounted in said housing ajacent said electromagnet and formed with a central opening throughwhich said key extends; a toroid-shaped permanent magnet loouly mountedin said housing adjacent said adherence disk and said key extendingthrough said pennanent magnet; a second disk loosely mounted in saidhousing adjacent said permanent magnet and attached to an end of saidkey, said end of said key formed with an opening; a magnetizable memberfixed to said housing and mounted such that when said key is in anundepressed position said magnetizable member is not in said openingformed in the end of said key and when said key is in a depressedposition said magnetizable member is within said opening formed in theend of said key; a magnetic-responsive switch contact attached to saidhousing and engageable with said magnetizable member when said key is inthe depressed position; means for energizing said electromagnet, a firstspring disposed in said housing between said adherence disk and said oneend of said housing and engageable with said key to bias said key to theundepressed position when said electromagnet is energized and mountedfor movement with said adherence disk when said electromagnet is notenergized, and including a second spring mounted in said housing betweensaid second disk and said housing to bias said key to the undepressedposition.

2. A key for a keyboard according to claim 1 wherein said housing iselectrically conductive and said magnetizable member is electricallyinsulated from said housing, and a pair of electrical conductorsconnected respectively to said housing and said magnetizable member.

t I! l i

1. A key for a keyboard for actuating a signal means comprising ahousing, a key supported for longitudinal movement in said housing andhaving a first portion which extends from said housing; an electromagnetfixed to said housing at one end thereof and said key extending throughsaid electromagnet; an adherence disk loosely mounted in said housingadjacent said electromagnet and formed with a central opening throughwhich said key extends; a toroid-shaped permanent magnet loosely mountedin said housing adjacent said adherence disk and said key extendingthrough said permanent magnet; a second disk loosely mounted in saidhousing adjacent said permanent magnet and attached to an end of saidkey, said end of said key formed with an opening; a magnetizable memberfixed to said housing and mounted such that when said key is in anundepressed position said magnetizable member is not in said openingformed in the end of said key and when said key is in a depressedposition said magnetizable member is within said opening formed in theend of said key; a magnetic-responsive switch contact attached to saidhousing and engageable with said magnetizable member when said key is inthe depressed position; means for energizing said electromagnet, a firstspring disposed in said housing between said adherence disk and said oneend of said housing and engageable with said key to bias said key to theundepressed position when said electromagnet is energized and mountedfor movement with said adherence disk when said electromagnet is notenergized, and including a second spring mounted in said housing betweensaid second disk and said housing to bias said key to the undepressedposition.
 2. A key for a keyboard according to claim 1 wherein saidhousing is electrically conductive and said magnetizable member iselectrically insulated from said housing, and a pair of electricalconductors connected respectively to said housing and said magnetizablemember.